Rubbing attachment for portable rotary power units



S. D. ROBINS Nov. 8, 1955 RUBBING ATTACHMENT FOR PORTABLE ROTARY POWER UNITS 4 Sheets-Sheet 1 Filed Feb. 12, 1953 Inventor Samuel 17. Robins S. D. ROBINS Nov. 8, 1955 RUBBING ATTACHMENT FOR PORTABLE ROTARY POWER UNITS 4 Sheets-Sheet 2 Filed Feb. 12, 1953 Nov. 8, 1955 s. D. ROBINS 2,722,739

RUBBING ATTACHMENT FOR PORTABLE ROTARY POWER UNITS Filed Feb. 12; 1953 4 Sheets-Sheet 3 3 nventor Samuel .D. Robins Bgwfmvfu'uy pm/ 4.

attorneys Nov. 8, 1955 s. D. ROBINS 2,722,789

RUBBING ATTACHMENT FOR PORTABLE ROTARY POWER UNITS Filed Feb. 12, 1955 4 Sheets-Sheet 4 Snveutors Samuel D. Robins (Ittorneus United States Patent RUBBING ATTACHMENT FOR PORTABLE ROTARY POWER UNITS Samuel Davis Robins, Lawrence, N. Y., assignor to Du-Fast, Inc., New York, N. Y., a corporation of New York Application February 12, 1953, Serial No. 336,47 9

4 Claims. (Cl. 51-170) This invention relates to sanding and rubbing machines and the like wherein the rubbing operation is secured by imparting to the rubbing medium an orbital motion with each point of the medium moving in a substantially circular path relative to the surface being treated. More specifically, the invention concerns a rubbing attachment for relatively low power power units for use in drilling for adapting of such units to surface smoothing and polishing operations and at the same time obtain rotary or gyratory motion of the rubbing surface.

Rubbing attachments for such low power power units are well known in the art, but these attachments have generally been found to be unsatisfactory for several important reasons. For instance, the average home workshop electric power unit for use in drilling is of relatively low power and rotates at speeds of about 1000 to 2000 R. P. M. Under these conditions, it is necessary for orbitual attachments to have a throw of about one half inch in order to attain peripheral speeds that are high enough to perform the work efliciently. Large throws necessarily entail a large frictional loss in the resilient members supporting the rubbing surface which varies in accordance with a multiple of the degree of displacement. Then too, a large displacement requires careful consideration of the design and manufacture of the resilient members in order to insure long life.

The above and other disadvantages apparent in known prior art devices have been overcome by this invention through provision of an attachment that not only reduces the orbital throw and, consequently, the substantial frictional losses but, at the same time, provides peripheral speeds of a high order even when the attachment is powered by a relatively low speed device.

Another object of the invention is a new and improved gear train assembly that can be coupled with generally available commercial power units for use in drilling, for driving rubbing attachments and at the same time permit the power unit to be positioned relative to the attachment so that the operator can apply substantially uniform pressure over the rubbing surface.

Another object of the invention is the provision of an orbital rubbing attachment for low power electric power units for use in drilling that is arranged and constructed to receive and hold any of a wide variety of such power units firmly and securely in position to drive the rubbing surface. it enables the joinder of the power unit and the attachment to provide a substantially unitary tool with the attaching means holding the power unit firmly notwithstanding the constant vibration to which it may be subjected, and at the same time provide for the quick release of the power unit when needed for other purposes.

Another object of the invention is an attachment for electric power units for use in drilling having a universal attaching means wherein the aligning and holding functions are substantiallyindependent and cooperate to provide an effective and secure joinder of the two devices.

A further object is a universal rubbing attachment for relatively low speed electric power units for use in drilling adaptable to receive and hold a large variety of such power units and produce high speed rubbing motion with relatively small movement of the rubbing head.

Another important aspect of this invention resides in an improved shaft coupling means cooperating with the power unit aligning and attaching means for providing a rapid connect and disconnect power coupling between the power unit and attachment. By reason of the particular structure of the coupling it may be installed in and removed from the power unit without straining or otherwise darnaging internal elements thereof and at the same time provide a positive driving connection between the power unit and the attachment that will compensate for minor alignment errors.

A further object is a new and improved rubbing attach ment for portable electric power units for use in drilling. The above and other objects of the invention will become more apparent from the following description and accompanying drawings forming part of this application.

In the drawings:

Fig. 1 is a side elevation of one embodiment of the invention with a portable power unit in position therein;

Fig. 2 is a plan view of the embodiment of Fig. 1 with the power unit removed;

Fig. 3 is a side elevation of the embodiment shown in Fig. 1 with the rubbing attachment illustrated in section;

Fig. 4 is a plan view of the speed changing assembly in accordance with the invention;

Fig. 5 is a side elevation of the assembly shown in Fig.4;

Fig. 6 is an exploded view of the elements of a coupling device in accordance with the invention;

Fig. 7 is a side view in partial section showing the coupling of Fig. 6 in the assembled position;

Fig. 8 is a bottom view of the assembled coupling shown in Fig. 6; and

Figs. 9A to C are schematic views showing certain characteristics of hand power units for use in drilling.

Portable electric power units for use in drilling, particularly those of the home workshop variety, though varying widely in size and shape, generally follow a similar fundamental arrangement of components. This can best be illustrated with reference to Figs. 9A to C inclusive, showing in schematic outline three shapes of such power units. In each of these figures the chuck shaft is denoted by the numeral 2, the armature by numeral 3 and the handle by numeral 4. It will be observed in Fig. 9A for instance that a plane Y defined by the axis of the shaft 2 and armature 3 bisects both the body of the unit and the handle 4. Notwithstanding certain differences in body contour of the units of Figs. 9B and C, the same condition obtains and each of the units is symmetrical about the plane Y.

It has been found that units of varying shapes and sizes can be securely held by means of an improved aligning member wherein two aligning edges are adapted to cooperate with the unit body to form a firm support therefor. In this way the unit can be held firmly in position merely with the aid of an adjustable encircling band. A bracket 19, according to the invention, is shown in Figs. 9A to C to illustrate its cooperation with a variety of unit housings. With this arrangement, although each type of unit housing rests in the bracket in a slightly different manner, there is always a double line contact with the housing that insures a stable support. These differences, coupled with commercial power units aforesaid to the advantage of the user of'the attachment.

The embodiment of the invention as shown in Fig. 1 illustrates in dotted outline a conventional electric power unit for use in drilling in position in the attachment to demonstrate the unique utilization of the foregoing parameters of electric powerv units to attain a dependable, efiicient and high. speed rubbing equipment particularly usefull in the home workshop as well as one. that can be produced at a relatively low cost.

This attachment includes a so-called stationary hollow body 10, a rubbing head 12 and a bracket and collar assembly 14 for holding the unit 16 in the body at a convenient operating angle.

With reference to Figs. 1 to 3, the hollow body is formed with a top surface 17 sloping upwardly toward the. front of the attachment at an angle substantially perpendicular to the desired angular position of the unit. As will be shown, this surface forms a base for mounting the unit and though it need not be made precisely perpend'icular to the unit axis, that disposition provides the most effective and desirable procedure. Surrounding the surface 17 of body 10 is a peripheral skirt 18 that protects and' shields the operating structure of the attachment with the exception of the rubbing head 12. By sloping the surface 17 as illustrated, the axis of unit 16 is tilted backward to. shift the. normal point at which pressure is applied to the handle rearwardly of the attachment to secure a more convenient operating angle and, together with handle 28, insure the application of uniform pressure on the rubbing shoe 12.

The universal attaching means is formed of two primary elements, namely an adjustable bracket 19 and an adjustable band 20. The bracket 19 cooperates with the surface 17 of body 10 to provide a positive aligning device adaptable to hold commonly available electric power units for use, in, drilling and comprises a U-shaped base portion 21 slidably mounted on surface 17 and longitudinally adjustable relative thereto. The adjustment is attained by means of a pair of bolts 22 passing through the legs 23 and 23 of the base 21 and cooperating with longitudinal slots 24. and- 24 in the inclined body surface 17. Extending upwardly from the U-shaped base 21 is an aligning member 19 positioned perpendicular to the bottom surface of they base 21 and having a pair of rearwardly extending guides or aligning edges 25 adapted to cooperate with the unit body and determine its alignment relative to the body 10. The bracket 19 in forming dual line contact with the body of unit 16 furnishes a secure, firm foundation. for the unit notwithstanding variations in the body contour and aligns the unit with its chuck shaft perpendicular to the-sloping surface 17. The unit is held firmly against the guides by an adjustable strap 20 encircling the. aligning bracket part 19 and the unit. It may be-tightened by any suitable clamping means such as the screw 26 and. adjustable cooperating clamp 27 so that as the screw 26 is rotated it tightens the band 20 firmly about the unit 16 and guide bracket 19 tohold the unit in proper alignment with the. attachment.

From the. foregoing description, it is apparent that the attaching means is not, only adaptable. for use with the power units aforesaidv of varying sizes and body shapes, but that it also compensates for varying positions of the axis of the chuck or driving shaft relative tothe-centerline of the unit b.ody.. The cooperation of the sloping body Moreover, as the an orbital path through' a. gear train 30in order to achieve desired high peripheral speeds of the rubbing head and at the same time effect a substantial reduction in frictional losses. This driving means, together with the resilient supporting assembly for the rubbing head 12 are housed within the body 10 and illustrated in Figs. 3, 4 and 5.

The gear train 30 is located centrally of the body 10 and on the underside of the body surface 17. The gear train includes a substantially dust proof housing 35 having a removable cover 36 to provide access to the gear elements 39 and 40. The housing 35 is secured within the body 10 by four corner mounts 37 formed integrally with the housing and cooperating with four screws 38 which extend through corresponding openings in the upper surface of the body 10. Within the housing 35 are a pair of coupled bevel gears 39 and 40 arranged to provide a speed ratio between the driving gear 39 and the driven gear 40 of 1:2. The gear 39 is preferably formed with an integral collar 41 having, a rectangular recess 42 to receive a corresponding coupling member 43 secured to and driven by the drill 16. Bevel gear 39 is rotatably retained in position by a flanged collar 44' and cooperating screw 4S'passing through a bushing 46 in the enlarged section 47 of the housing 35. The collar 44 is formed with a rectangular flange, for cooperation with the rectangular recess 42 and also includes internal threads for receiving the threaded end portion of the screw 45. The smooth shank 48 of the screw rides within the bushing 49 in opening 46 to form the rotatable support or hearing for the gear 39.

The gear 40 is held in engagement with gear 39 within the housing. 35 by means of a ball bearing assembly 50. contained. within a suitable recess formed in the under side of housing 35. A shaft 51 having threaded end portions 52 and 53 is snugly fitted within the internal race of bearing with the threaded end 52 carrying the gear 40 and the opposing threaded end 53 carrying the rubbing shoe drive and counterweight 54. The axis of gear 40 and shaft 51 is generally perpendicular to and in approximate alignment with the mean center of gravity of the rubbing shoe 12. The axis of gear 39 on the other hand is perpendicular to surface 17 of the body 10 and positioned forwardly of the center of body 10 to receive the driven coupling 43 of the drill 16. The displacement of gear 39 from. the center of the attachment is coordinated with the general structure of power driven tools as set forth above and with the aligning and securing bracket member 14' to accommodate a wide variety of powered devices such as the hand power unit 16 and like equipment. While the chosen embodiment of this invention includes a gear train, it is apparent that similar ends may be attained by belt or friction drives well known in the art.

The resilient shoe. supporting structure generally surrounds the gear train. 30 and is but one of many ways in which the shoe 12 can be secured to the body 10 for orbital motion relative thereto. This structure is disclosed in U. S. Patent No. 2,614,369 and comprises a pair of upper parallel flexible links 32 of belting or like material that depend from the ends of housing 35 and are fastened thereto by elongated angular members 55 and screws 56. The intermediate frame 33 comprises parallel side and end rails 57 and 58 preferably of metal or other light weight material that will form a rigid open frame. The end rails 57 are clamped firmly to the lower edges of the flexible links 32 and the side rails 58 similarly clamp the upper edges of the lower set of links 34 displaced approximately ninety degrees from the links 32.

The live. frame or rubbing shoe is attached to the lower resilient members 34 by means of upwardly extending elongated flanges 59, screws 60 and cooperating metal strips 61. The. brackets 59 are carried by the shoe pressure plate 62 which has its ends. bent upwardly to hold the sandpaper or other rubbing material 63. A pad 64 of rubber, felt or like material is cemented or bonded to the pressure plate 62 and provides a cushion between the rubbing surface and the pressure plate in order to compensate for slight irregularities that may exist in the surface being treated. The upwardly bent end portions 65 function with Spring loaded latch members 66 to stretch the sandpaper 63 over the resilient surface 62 and then hold the sandpaper in place during the rubbing operation.

The rubbing head 12 is driven in its orbital motion by means of the crank pin 67 on the counterbalanced driving head 54. This crank pin is displaced from the centerline or axis of the pin 51, a distance equal to about /2 the desired throw or about As". It engages a central opening 68 in the ball bearing assembly 69 which in turn is carried in a recess 70 formed integrally with the pressure plate 62 and at the approximate center of gravity of the shoe or rubbing head 12. A major portion of the vibration produced in the body by reason of the orbital drive is substantially cancelled by the counterweight 71 which produces a force equal in magnitude to that of the shoe 12 but of opposite direction.

Figs. 6, 7 and 8 illustrate the quick disconnect coupling for use with the unit 16 to drive the attachment. It includes a threaded rod-like member 72 having a hexagonal recess 73 in one end thereof to receive a hexagonal wrench 76 and a rectangular cap 43. The cap is formed with an internal threaded opening 74 to receive the screw 72 and an opening 75 extending through the end of the cap and in alignment with the threaded passage 74. This arrangement provides a quickly removable coupling that can be readily substituted for the chuck normally carried by the shaft 16a of unit 16. Toinstall this coupling, the chuck is removed from shaft 16a, the threaded member 72 is substituted therefor and the cap 43 is then screwed in place on the outer end of the threaded member until its shoulder 43a contacts the end of shaft 16a. The wrench 76 is then inserted through opening 75 to engage the recess 73 and a conventional end Wrench can then be used on the rectangular portion of the cap to rotate it relative to the screw 73 to lock the cap 43 in position on shaft 16a. The reverse procedure will function to release the coupling without straining internal parts of the unit, as in the release of conventional couplings wherein the inertia of the unit parts is relied upon to react against a releasing stress placed on the coupling.

While substantially perfect alignment of the coupling 43 with the recess 42 in gear 39 normally can be attained by careful adjustment of the bracket 14 relative to the body surface 17, provision is made to compensate for slight errors and yet attain a smooth vibrationless' drive. To this end, the surfaces of the rectangular coupling head 43 are slightly curved as may be observed at 78 (Fig. 7) to effect a slight degree of universal movement. With this arrangement, play is reduced to a minimum without incurring any binding stresses and substantial power losses. In addition, one or more of the gears within housing 35 may be formed of a tough nonmetallic material such as glass-fiber and the like to further reduce noise and damp vibrations that may be reflected back to the unit 16 from the rubbing head 12.

The invention in its broader aspects is not limited to the specific mechanisms shown and described but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

1. A rubbing attachment for electric power units for use in drilling which are generally symmetrical about the plane of the armature and chuck axes of the power unit, said attachment comprising: a body having a top surface provided with an opening adapted to receive said power unit; a rubbing head to be driven by the power unit, said head being supported by the body for rubbing movement in a prescribed path; and, universal attaching means carried by said body for receiving and holding any of a wide variety of said electric power units firmly and securely in a selected fixed driving position in said opening in said top surface, to drive said rubbing head, said means comprising an aligning and securing bracket adjustably mounted on said body and having spaced apart aligning portions for engaging the housing of the power unit at opposite sides of the said plane of symmetry of the power unit, and an adjustable clamping band carried by said bracket member for encircling the body of the power unit and holding the power unit firmly against said aligning portions.

2. A rubbing attachment for electric power units for use in drilling which are generally symmetrical about the plane of the armature and chuck axes of the power unit, said attachment comprising: a body having a sloping top surface provided with an opening adapted to receive said power unit; a rubbing head to be coupled to and driven by the power unit, said head being supported by the body for rubbing movement in a cyclic path; and, universal attaching means for receiving and holding any of a wide variety of said electric power units firmly and securely in a selected fixed driving position in said opening, to drive said rubbing head, said means comprising an aligning and securing bracket slidably mounted on said sloping top surface in longitudinal- 1y adjustable relation thereto, said bracket having a pair of spaced apart substantially parallel aligning edges for engaging the housing of the power unit in dual line contact therewith at opposite side of the said plane of symmetry of the power unit, and an adjustable clamping band carried by said bracket member for encircling the body of the power unit and holding the power unit firmly against said aligning edges.

3. A rubbing attachment for low power electric power units for use in drilling which are generally symmetrical about the plane of the armature and chuck axes of the power unit, said attachment comprising: a body having a sloping top surface provided with an opening adapted to receive said power unit, said surface sloping upwardly toward the front of the attachment as an angle at which said surface will be substantially perpendicular to the desired angular position of the power unit; a rubbing head to be coupled to and driven by the power unit, said head being supported by said body for rubbing movement in an orbital path; and, universal attaching means for receiving and holding any of a wide variety of said electric power units firmly and securely in a selected fixed driving position in said opening, to drive said rubbing head, said means comprising an aligning and securing bracket having a U-shaped base portion slidably mounted on said sloping top surface in longitudinally adjustable relation thereto and a power unit-aligning member extending outwardly from said base portion, said power unit-aligning member having a pair of rearwardly extending spaced apart substantially parallel aligning edges for engaging the housing of the power unit in dual line contact therewith at opposite sides of the said plane of symmetry of the power unit, said aligning edges being in substantially perpendicular relation to said sloping top surface, and an adjustable clamping band carried by said power unit-aligning member for encircling the power unit body and holding the power unit firmly against said aligning edges.

4. A rubbing attachment as claimed in claim 3 including adjustable fastening means between each leg of said U-shaped base portion and said sloping top surface, for releasably securing said universal attaching means to said body.

References Cited in the file of this patent UNITED STATES PATENTS 1,741,145 Drennon Dec. 31, 1929 (Other references on following page) 8 Happe Mar. 22, 1949 Asbury Oct. 4, 1949 @910 Jan. 3, 1950 Sheldon Mar. 21, 1950 Robins Oct. 21, 1952 FOREIGN PATENTS Germmy Aug. 23, 1926 

